Physicist's experiments resolve nature of neutrinos

As a graduate student Peter Wittich, associate professor of physics, worked at the Sudbury Neutrino Observatory (SNO), located in an active nickel mine in Ontario, Canada. The observatory is deep underground to block out background radiation from other particles.

To reach the clean room and the SNO instruments, Wittich descended 6,800 feet straight down through solid rock in a tiny elevator, then walked a mile through either ankle-deep mud or air so dusty that visibility was only a few feet ahead.

That dedication paid off when, on Wittich’s 29th birthday, the SNO detected its first neutrino, setting the stage to prove that the sub-atomic particles do indeed have mass.

“We could already see from this beginning what the results of the larger experiment would be – the discovery for which Art McDonald just received the [2015] Nobel Prize – but I couldn’t say anything for years after my thesis was written, until the collaboration felt the data was sufficient for the discovery to be announced,” says Wittich. “At times it was touch and go, but in the end the experiment worked beautifully and we were able to resolve a 30-year mystery about how the sun works and the nature of neutrinos.”

Wittich and his group built the bulk of the electronic instrumentation that collected the data for the SNO; the experiment required a tank containing 10,000 tons of water. Ironically, Wittich says he “stumbled” his way into experimental physics. “On my first day after joining a research group in graduate school a professor said, ‘I hear you’re interested in instrumentation.’ I didn’t know what that was, but I thought I’d better say yes.”

That answer determined Wittich’s future. Decades later, he is still building electronics.

“When people think about physics, they think about a guy with a pencil and paper,” he says. “But physics is an experimental science.”

After SNO, Wittich moved on to Fermilab, where he continued studying the fundamental nature of particles, working with a team of 700 scientists. He’s now at the European Organization for Nuclear Research (CERN) working with the Large Hadron Collider (LHC) and a team of 3,000. The large team is necessary, Wittich says, because of the enormous complexity of the LHC.

“We’re at the forefront of big science. We work collaboratively to build the instruments, then use the data individually to try to understand the particular characteristics of particles we already know or to find new particles. But every one of the papers has the same 3,000 authors in the same order, because building the apparatus and collecting the data was the huge work.”

That data is created, Wittich explains, by colliding a beam of protons 40 million times a second. The researchers collect tens of petabytes of data a year (there are a million gigabytes per petabyte).

Right now Wittich is working with four Cornell researchers, postdoc Livia Soffi and graduate students Jorge Chaves, Margaret Zientek and Kevin McDermott, to find evidence of dark matter in the LHC results.

“The scale of energy ought to be right to find it at CERN,” says Wittich. “This is a really exciting time to be doing physics.”